What Age Do Quarter Horses Stop Growing?

The American Quarter horse received its name from its unique talent to outrun other types of horses in a quarter of a mile or less. These horses are very agile and quick on their feet, with the fastest quarter-mile sprint clocked at 55mph (88.5kmh).

Quarter horses stop growing when they are about four or five years old. Most of a horse’s growth happens in the first year of their life, almost 90%, after which their growth rate slows down considerably until they become fully grown. One thing that is fully grown after the first year is a horse’s legs. Their bodies and heads then continue to develop until they are fully grown.

A horse’s size and growth rate depend on various factors, including the type of breed and quality of life, so let’s have a closer look at Quarter horses compared to other horse breeds.

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Quarter Horses vs. Other Horse Breeds

There are more than 200 different horse breeds in the world, and you can actually identify them by the way they look, with three main body types, ponies, light breeds, and heavy breeds.


Ponies are short and stocky, with a maximum height of 58 inches and weighing between 200 and 1500 pounds. Their manes are very thick, and they have shorter faces and legs than other horses.

People used to breed ponies to drive carts, but today they are great for children to ride because they are smaller, friendlier, and also the most intelligent of the horse types.

Today, there are also competitions for ponies to show off their own great characteristics.

Heavy Breeds

These horses are big and powerful, with an extremely muscular body, thick legs with heavy feathering, broad shoulders, and a shorter back.

Heavy breeds, or Draft horses, are workhorses that pull plows and haul heavy loads. A draft horse weighs between 1400 and 2700 pounds and grows up to 64 to 76 inches.

Light Breeds

Then there are the light breeds, which are, well, light and fast. Quarter horses are light breeds, with thin legs, long necks, and distinct withers — the part of the spine between the shoulder blades that supports the horse’s neck (source).

A true American breed, Quarter horses are used by ranchers to handle cattle because of their speed over short distances, their quick footing, and high intelligence.

These horses are who they are today due to a blend of thoroughbred bloodlines that were known for their speed, agility, and temperament. Quarter horses are also favorites in show jumping, combined training, and rodeos.

The three types of Quarter horses you will find include a bulldog type, the Thoroughbred type, and then also an intermediate type that sports the characteristics of the other two.

Quarter horses have 17 recognized colors but are most often sorrel or chestnut, with the same color, black, or flaxen mane and tail.

An interesting fact when talking about horses is that you identify them by first their color, then breed, and then gender, for example, a sorrel Quarter horse stallion (source).

We can also identify a Quarter horse by its thin legs, powerful hindquarters, wide chest, and a straight face.

Measuring Growth and Age

Horses do the lion’s share of their growing in the first year of their lives, and their legs reach their full length in that year. After a year, it’s really just the rest of the horse’s body and head that still needs to grow.


We measure Quarter horses, and other horses in general by the height of their withers, using horse hands.  Like I explained before, withers are the highest part of a horse’s back, between the shoulder blades.

Basically, this means that when a horse is bending its neck to the ground, this part of its body is the highest point.  A Quarter horse’s withers usually measures at 14.3 to 16 horse hands.

Horse hands, which are four inches, is an archaic measurement that people have been using since ancient Egypt — horses have been around for at least that long, and people don’t let old habits die easily.

Because Quarter horses’ legs, as well as those of most horses in general, are fully grown by the time they are one or one-and-a-half years old, and they are usually twice as tall as their legs, you can predict how tall a yearling will become one day by measuring its legs and doubling that. It’s not an exact science but will give you a general idea (source)


Quarter horses and other light breeds are fully grown by the age of four or five years old, although larger breeds can take up to six or seven years to fully mature, with a life span of 25 to 30 years. The record of the oldest horse that people could verify was 62 years!

The best way to figure how old your Quarter horse is would be by looking at its teeth. Yes, that’s what I said — its teeth. We usually look at the incisors or the 12 teeth that are in the front of their mouths.

Of course, when horses are still babies, they don’t have all their teeth and this is also an indication of their age. Just like humans, your Quarter horse also has milk teeth, which they lose as they grow older.

A horse’s teeth not only change in size but also in color and shape. You will also find cups, or indentation, on the permanent teeth of young horses. These cups disappear as the horse ages.

With older Quarter horses, we can also inspect what they call Galvayne’s groove, which is a groove on the tooth surface that starts at the gumline and moves down toward the bottom of the teeth over time. This usually starts happening at around age 10.

At the age of 15, a Quarter horse’s Galvayne’s Groove should be about halfway down its teeth, and from around 20 years old, Galvayne’s Groove starts disappearing from the top (source).

Quarter Horse Life Stages

Image by Andreas Krappweis via FreeImages

Foal to Weanling

A baby horse is called a foal and stays close to its mother because it nurses not just frequently — try three to five times an hour!

Foals also tend to eat their mother’s poop in the first two months of their lives. Euw! It’s called coprophagia and, apparently, it’s normal, even for adult horses to do in small quantities.

This is the age when the little one needs to get used to grooming and handling and even wearing a halter.

At three to six months, the foal weans off its mother’s milk, and we can now call it a weanling. At this stage, horses are already half of their mature physical size and need lots of exercise with proper nutrition to build strong muscles and bones.

Once a weanling is no longer feeding from its mother anymore, they are also ready to learn how to interact with others, so it is important for them to have contact with other horses and people at this point.

Yearling to Adolescent

Between the ages of one and two years, yearlings are awkward with an almost mature height, but their bodies still need to catch up. This is the time when horses start exploring and getting really curious about their surroundings.

Once horses hit puberty, between two and three years, they stop growing so fast and can start their training because they are more emotionally mature as well and will be able to understand instruction better. Female horses are fillies, and the males are called colts.

Horses are natural grazers and do this when they are hungry or just bored. If there’s no grass, they will explore and even chew on tree bark or branches. Best to keep the horses well-fed because their curiosity could get them into trouble with any poisonous plants or trees.

Adults to Seniors

Fillies and colts become mares and stallions (or geldings) once they reach full physical maturity. As adults, they can now breed and do much more work because they are emotionally also more mature.

Horses reach their physical peak between 10 and 20 years, and this is the time where they can do their best work.

After that, they start to really get old when they hit their twenties, and horse owners need to take special care of them. They can’t keep themselves as warm as they used to anymore and also need to eat softer food.

Image by Andreas Krappweis via FreeImages

Final Thoughts

Quarter horses are a truly American breed of horse that people bred especially for their speed, their intelligence, and their intuitive nature. Their name comes from their superpower to outrun other horses in a quarter of a mile or less.

These horses, like most other horses, only reach full physical maturity at the age of four or five years old, even though most of their growth happens in the first year of their lives.

Quarter horses play an exciting role in society at rodeos, in show jumping, and combination training as well as helping with herding cattle. They need to be well taken care of with the right food, enough nutrition, plenty of exercise, and lots of love.

They are powerful, smart animals that are so much more than a pet in need of a certain standard of care and maintenance.

In a way, horses are a lot like people, though they do not live as long as we do.